1. Field of the Invention
The present invention relates to an easy open type container wherein an opening is tightly covered with a closure member made of at least a metallic foil. More particularly, to a container with an easy open type closure in which a pull-opening member is provided at its initial end portion with a pulling tab connected more firmly to the closure member than the tearing strength of the closure member, so that the closure member can be torn open by way of the pull-opening member by pulling the pulling tab upwards in relation to the closure member.
2. Description of Background Art
As for a container of this kind, there has been hitherto proposed by the inventors of the present invention a closure as shown in FIGS. 8 and 9 and disclosed, for instance, in Japanese Unexamined Utility Model Registration Application Publication Sho 57 (1982) - 177932. A closure member a shown in FIGS. 8 and 9 is made of a lamination comprising a metallic foil such as an aluminium foil or the like and a thermoplastic synthetic resin layer. The closure member a is applied to cover an opening of a container barrel body c and is fixed, by curling fastening or fusion adhesion, to an edge of the opening of the container barrel body c through a ring-shaped member b which is made of metal or synthetic resin. A pull-opening member f comprising a circular strip member made of thermoplastic synthetic resin or the like and having at its initial end portion a pulling tab e is applied and fixed to an area of an upper surface of the closure member a that is inside an inner edge d of the ring-shaped member b by fusion adhesion or through an adhesive agent more firmly than a tearing strength of the closure member a.
In order to tear the closure member a open, the pulling tab e is held between one's fingers and pulled upwards in relation to the closure member a, an initial tearing opening of the closure member a is made by the initial end g of the interconnection portion j. If the pulling tab e is further pulled upwards together with the pull-opening member f, the tearing of the closure member a is torn open along the inner edge d of the ring-shaped member b. In this manner, the lifting force of the pulling tab e acts to deform a flat condition of the closure member to result in generation of a resistance force, because the pull-opening member f is fixed so firmly as mentioned above to the closure member a.
If the pull-opening member f has such a high rigidity that transmits a force to the whole length of the pull-opening member f even in the case of a partial slight deformation thereof, the foregoing resistance force turns into a resistance force generated over the whole length of the pull-opening member f. Thus, the foregoing initial tearing opening cannot be made by a small pulling force. This results in an inconvenience in that it is difficult to easily tear open the closure member by children.
On the other hand, if the initial end g of the interconnetion portion j is not firmly fixed to the closure member a, an inconvenience occurs in that the pull-opening member f is peeled off from the closure member a. If the pull-opening member f and the pulling tab e connected to the initial end thereof are substantially equal one to another in thickness, a comparatively large pulling force is required for largely lifting the pulling tab e upwards at and about the initial end g of the interconnection portion j between the pull-opening member f and the closure member a, so that the foregoing inconveniences are increased. If the lifting of the pulling tab e is continued after the foregoing initial tearing opening is made, the closure member a undergoes a tearing advancing along a guide edge h provided on the pull-opening member f to reach the inner edge d of the ring-shaped member b and a tearing starting with a point X and advancing along an inside edge i of the pull-opening member f. If the lifting of the pulling tab e is further continued, the tearing which has reached the edge d is advanced along the inner edge d, while the tearing advancing along the inside edge i is advanced until it goes nearly half round, but the advancing of the tearing is stopped when the center region of the closure member a is loosened. Accordingly, the subsequent tearing stress is concentrated only on the portion extending along the inner edge d, and as a result only the tearing along the inner edge d is continued to the last, so that a complete circular opening of the container can be obtained.
However, when the pulling tab connected to the initial end of the pull-opening member f is not properly positioned in its pulling direction, it often happens that accurate tearing along the inside edge i cannot be made and the tearing advance is stopped before it proceeds halfway around. Consequently, sufficient looseness of the closure member a cannot be obtained, and accordingly the tearing stress does not concentrate only on the opening edge d. As a result, tearing occurs at an intermediate area between the inner edge d and the pull-opening member f, and there remains a piece of the closure member a which is unremoved in a position along the inner edge f so that tearing is advanced about 180 turning degrees from the initial tearing opening as shown by imaginary lines in FIG. 8.